Let a, b, and c be sets. Prove that (b − a) ∪ (c − a) = (b ∪ c) − a by showing that each is a subset of the other. What is the correct proof for this set equality?

A) (b − a) ∪ (c − a) ⊆ (b ∪ c) − a and (b ∪ c) − a ⊆ (b − a) ∪ (c − a)
B) (b − a) ∪ (c − a) ⊆ (b ∪ c) − a but not (b ∪ c) − a ⊆ (b − a) ∪ (c − a)
C) (b ∪ c) − a ⊆ (b − a) ∪ (c − a) but not (b − a) ∪ (c − a) ⊆ (b ∪ c) − a
D) (b ∪ c) − a ⊆ (b − a) ∪ (c − a) and (b − a) ∪ (c − a) ⊆ (b ∪ c) − a